Conventional torsional flexible connections consist of two hubs between which a flexible (deformable) member is located. The flexible member can be continuous, and loaded in shear such as in tire couplings, or can be composed of several discrete elements loaded in compression (e.g., see E. Rivin, "Design and Application Criteria for Connections Couplings", in ASME Journal of Mechanisms, Transmissions and Automation in Design, 1986, Vol. 108, No. 1, pp. 96-105). Usually the former types of flexible torsional connections (with shear deformation of the deformable member) have a relatively high torsional flexibility, but a relatively low payload capacity for a given size. The latter types (with compression deformation of the deformable member) have a relatively high payload capacity for a given size, but a relatively low flexibility (high torsional stiffness), as it is also demonstrated in the above-referenced article. Some torsional flexible connections exhibit non-linear load-deflection (torque-angular deformation) characteristic which is beneficial for many applications as it is demonstrated in the above-referenced article. However, non-linear torsional flexible connections known in the art (e.g., MAX C "CB" from Kop-Flex Company) have a relatively low payload capacity for a given size.
Flexible torsional connections of the above outlined types are normally used as flexible couplings for connecting nominally coaxial shafts. Numerous flexible coupling designs are known which can transmit substantial torques while having reasonably small dimensions, but at the price of low torsional compliance, e.g. so-called jaw couplings represented by teachings of U.S. Pat. No. 3,638,454 in which rubber flexible inserts conform with the chambers into which they are inserted thus restricting deformation of the inserts under the transmitted torque, but allowing to accommodate high forces and, consequently, torques. Other designs have extended torsional flexibility (required in many applications for reducing transient overloads and torsional vibrations), but at the price of a reduced rating, i.e. of reduced torque-transmitting capability for a given size, thus requiring large and costly installations. A representative of this group is Dynaflex family of couplings from Lord Corporation in which an annular rubber elastic element is undergoing shear deformation.
Large size for a given rated torque prevents designers from using conventional flexible couplings as flexible hub-to-rim connections in such power-transmission elements as gears, sprockets, pulleys/sheaves which frequently require such connections for reducing dynamic loads in the mesh (and, consequently, for increasing rated payload capacity of the gears), for reducing or modifying torsional vibrations in the transmissions, and for reducing noise. Another factor preventing use of conventional flexible couplings for hub-to-rim connections is their inevitable radial compliance unacceptable for gear/sprocket applications. Attempts to reduce radial compliance (i.e., increase radial stiffness) by changing characteristics of a conventional connection lead to undesirable increase in its torsional rigidity (e.g., see the above referenced article).
In short, none of the prior art patents or trade publications serve to satisfy a need for a reasonably compact torsional flexible connection which can transmit high payloads, has high torsional flexibility, has non-linear torque-angular deformation characteristic, and can be used both as a torsionally flexible coupling and as a torsionally flexible, but radially stiff hub-to-rim connection for power-transmission gears, etc.
The present invention addresses the inadequacies of the prior art by providing a torsional flexible connection whose hubs have sets of equidistant protruding blades which are interdigitated to form wedge-shaped chambers housing flexible inserts loaded in compression by the transmitted torque. Each insert is comprised of two or more elements of streamlined shapes, whose dimensions in the load-transmitting (circumferential) direction are proportional to their distances from the axis of the connection, thus providing the same intensity of deformation for all the elements and assuring sharing by them the load transmitted by the connection. This allows to increase load-carrying capacity of the connection for a given size. The streamlined shapes of the elements lead to their non-linear load-deflection characteristics, and also to reduced stress concentrations. This, together with better heat transfer from several smaller elements as compared with the larger single elements, allows to increase allowable cyclic deformation amplitudes thus further increasing both rating and torsional flexibility for a given size of the connection. High radial stiffness in cases when the connection is served as a hub-to-rim connection is provided by thin-layered rubber-metal laminated inserts between the two hubs of the connection. The rubber-metal laminates are known to combine very high compression stiffness (utilized in the radial direction of the connection) and very low shear stiffness (utilized in the circumferential direction of the connection).
These and other advantages of the present invention will be readily apparent from the drawings, discussion, and claims which follow.